Catechins are reported to have a suppressing effect on the increase of cholesterol and an inhibitory effect on α-amylase activity (see, for example, Patent Document 1 and Patent Document 2). For such physiological effects to materialize, it is necessary for an adult to drink 4 to 5 cups of tea a day. Therefore, there has been a demand for a technology that can make a beverage contain catechins in high concentration, so that a large amount of catechins can be consumed with ease. As one of such examples, there is a method that is designed to incorporate catechins into a beverage in a dissolved form by using a concentrate of green tea extract or the like (see, for example, Patent Documents 3 to 5).
However, if used in the raw, commercially available concentrates of green tea extract result in strong astringency and bitterness attributable to the components contained in such concentrates of green tea extract and cause a poor feeling when running down through the throat. From the standpoint of applicability for long-term drinking that is needed for the physiological effects of catechins to arise, there has been a demand for a beverage that can be stable over a long period of time and satisfies both of the requirement for adequate sweetness and sourness and the requirement for reducing the astringency originated from catechins characteristic of a beverage with a high concentration of catechins, whatever its technique.    [Patent Document] JP-A-60-156614    [Patent Document] JP-A-03-133928    [Patent Document] JP-A-2002-142677    [Patent Document] JP-A-08-298930    [Patent Document] JP-A-08-109178